There is an extending discussion in the Harvard Law Review Foreword about Empirical Fact Finding:

This pattern is, in fact, a conspicuous feature of the Court’s constitutional ju-risprudence generally. In cases involving sex equality, gay rights, the death penalty, police seizures, drug testing, and other charged matters, the Court has invoked empirical evidence—or sometimes the lack of it—as warrant for its decisions. When it does so, the genuineness of its reasoning has provoked accusations of bad faith, not only from within the court but from without.169

There are many potential explanations for this recurring form of empirical-point, denunciation-counterpoint. When Justices rely on empirical data in contro-versial decisions, they no doubt often honestly believe that such evidence compels a particular result. If so, it’s possible that their perceptions, those of their critics, or both could be influenced by motivated reasoning.170 The impact of motivated

reasoning on the Justices themselves could also explain apparent discrepancies across cases in how the Court treats standards of review 171 or other doctrines re-levant to the impact of empirical proof—including whether it is appropriate for judges to consider “empirical data” at all.172 It’s also likely, though, that the Court sometimes consciously resorts to em-pirical factfinding for strategic reasons.173 The Justices might well believe that their decision—particularly if it is likely to disappoint one side or the other on an issue that is the focus of cultural status competition—will provoke less conflict, or impose less insult on the losing side, if framed in the seemingly neutral idiom of fact rather than in the morally evocative idiom of constitutional principle.174 The contribution empirical arguments are thought to make to muting contested values is part of their appeal in political discourse generally.175 If the prudential concerns of this sort are motivating them, the Justices needn’t be viewed as using empirical evidence to “hide” their reliance on their partisan values. More likely they are try-ing to avoid invoking one or another of the Constitution’s liberal principles in a manner that could be understood as denigrating a particular group’s vision of the good life—as opposed to merely placing a barrier between any particular group’s vision and obligations that are legitimately enforced on all.

This passage seems quite apt to the competing debates about the Second Amendment:

The only citizens who are likely to see the Court’s decision as more authorita-tive and legitimate when it resorts to empirical fact-finding in culturally charged cases are the ones whose cultural values are affirmed by the outcome. If they were not already impelled by identity-protective cognition to believe the “facts” in ques-tion before the decision, they will be after by the Court’s designation of them as “objective” and appropriately “neutral” grounds for their position. These citizens will thus react defensively and dismissively in response to those who dispute those facts—whether dissenting Justices, unpersuaded academics, or other citizens—and will suspect them of duplicity and self-delusion.

On Scalia’s “extraoridinary dissent” in Plata:

In effect, Scalia is telling us to wise up, not to be snookered by the Court. Sure, people claim that their “policy positions” on matters such as crime control, fiscal policy, and national security are based on empirical evidence. But we all know that things are in fact the other way around: what one makes of empirical evidence is “inevitably” and “necessarily based . . . upon policy views.”189 At one point, Scalia describes the district court judges as having “dress[ed]-up” their “pol-icy judgments” as “factual findings.”190 But those judges weren’t, in his mind, doing anything different from what anyone “inevitably” does when making “broad empirical predictions”: those sorts of “factual findings are policy judgments.”191 Empirical evidence on the consequences of public policy should be directed to “legislators and executive officials” rather than “the Third Branch,” Scalia in-sists.192 The reason, though, isn’t that the former are better situated to draw relia-ble inferences from the best available data. On the contrary, it is that it is a conceit to think that reliable inferences can possibly be drawn from empirical evidence on policy consequences—and so “of course”193 it is the “policy preferences”194 of the majority, rather than those of unelected judges, that should control.

For my own thoughts on Plata and experts, see here and here.

On Heller:

The Court actually did something like that, I believe, in District of Columbia v. Heller. 350 In Heller, the Court paints a richly detailed picture of guns and civic vir-tue in the early Republic, and discovers within it an individual “right to bear arms” that extends to possession of a handgun for personal self-defense in the home.351 But the opinion, written by Justice Scalia, doesn’t end with that. Rather, it proceeds to outline a surprisingly detailed list of the sorts of arms-bearings to which the Second Amendment right does not extend. “Like most rights, the right secured by the Second Amendment is not unlimited,” the Court states.352 “From Blackstone through the 19th-century cases, commentators and courts routinely explained that the right was not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose.”353 “For example,” the opi-nion continues, “the majority of the 19th-century courts to consider the question held that prohibitions on carrying concealed weapons were lawful under the Second Amendment or state analogues.”354 The Court added that “nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms.”355 Thus, in disregard of its usually scrupulous avoidance of “advisory opinions,” the Court had effectively identified a capacious safe harbor for continuing regula-tion. And lest anyone think to try an expressio unius est exclusio alterius maneuver on these passages, the Court added in a footnote: “We identify these presumptively lawful regulatory measures only as examples; our list does not purport to be exhaus-tive.”356 Likely added to the opinion to nail down Justice Kennedy’s critical fifth vote, this language nevertheless placed an expressive-overdetermination shield between the Court and the dueling cultural constituencies that were most likely to question its neutrality. Guns have tremendous expressive significance for individuals with hierarchical and individualistic values, for whom they enable roles like father and protector, and symbolize virtues like honor, courage, and self-reliance. By the same token, guns are anathema to citizens with egalitarian and communitarian val-ues, who associate them with patriarchy, Southern resistance to civil rights, and societal distrust.357 The consequences of gun control for health and safety are ge- 350 554 nuinely ambiguous. 358 But the consequences of the gun control debate for the sta-tus of those subscribing to these cultural outlooks has been clear for decades.359 As a result of the safe-harbor language in the Court’s opinion, the victory of the hierarchical individualist position in Heller did not equate to a complete defeat of the egalitarian communitarian side.

But even more important, the crafting of the opinion made it doubtful that either side could be put in a position of domination at the hands of the other in the future. The safe-harbor language left the egalitarian communitarians free to continue seeking regulation of guns; indeed, it remained open to them, the Court was making clear, to continue opposition to concealed carry laws, which had been at the heart of the battle to control the expressive capital of gun laws for decades. Yet whatever they might achieve at this point would be constrained by the consti-tutional individual right to own a gun. Woven out of the civic republican cloth of Founding era mythology, the simple articulation of that right conferred on gun owners the unequivocal and durable recognition of status that Justice Kennedy had wanted the Court to give abortion opponents in Hill. Without being denied the power to participate in the continuing political conversation about guns, egali-tarian communitarians would not after Heller be able to make the law speak in a denigrating voice.360